Heterogeneous organotin catalysts

ABSTRACT

Supported heterogeneous organotin catalysts of the formula X1, X2, or X3: 
     
       
         
         
             
             
         
       
         
         
           
             wherein Z is a spacer group; 
             Y is an insoluble phenyl-group containing copolymer; 
             R 1 , R 2 , R 3 , R 5 , and R 6  are independently selected from halogen, alkyl, alkylene, phenyl, vinyl, allyl, naphthyl, aralkyl, and Z; and 
             R 4  is alkyl, alkylene, phenyl, vinyl, allyl, naphthyl, or aralkyl.

This application is a divisional of and claims priority to U.S. patentapplication Ser. No. 11/099,868, filed Apr. 5, 2005 now U.S. Pat. No.7,687,581, the entirety of which is incorporated herein by reference.

The present invention relates to supported heterogeneous organotincatalysts, particularly this invention relates to a process for thepreparation of supported organotin catalysts, polymer-supportedorganotin catalysts for esterification and transesterification reactionsand a process for conducting esterification or transesterificationreactions.

Homogeneous organotin compounds are known to be effective catalysts fora variety of reactions in the organic chemistry. Organotin compoundsshow interesting properties as catalysts in organic and siliconchemistry. In these fields, they are mainly used in esterifications,transesterifications, transcarbamoylations for the preparation ofpolyurethanes, and for the curing of silicones. For this purpose, oftenmono- and diorganotins are used. Heteroatoms linked to tin can behalides, mainly chlorides, hydroxides or carboxylates. In some cases,mixed halide-hydroxides are the most efficient. Among the advantages oforganotin catalysts with respect to others, their very high efficiency,high selectivity and high activity at low concentration are oftenstressed.

However, homogeneous organotin catalysts are sometimes either difficultto eliminate totally from the products or cannot be removed at all. Itis thus one objective of the present invention to provide new andefficient ways to separate chemicals as efficiently as possible from theorganotin compounds involved in their preparations. Among all thepossibilities to achieve this goal, the use of heterogeneous catalystsis provided by this invention. Whereas homogeneous catalysts are in thesame phase as the reactants and reaction products (usually liquid),heterogeneous catalysts are of a different phase than the reactionproducts. In this way, the organotin catalysts can be removed easilyfrom a liquid reaction mixture by filtration or decantation orsedimentation or similar phase separation steps after reaction.

A variety of different heterogeneous catalysts is known. They have anumber of significant advantages over homogeneous catalysts such as easeof separation of the catalyst from reaction products enabling thepossibility of re-use and recycling of the heterogeneous catalyst.Whereas some heterogeneous catalysts are sometimes not as selective ashomogeneous catalysts, supported heterogeneous catalysts with the activespecies attached to the support by a chemical bond, are often describedas being as selective as their corresponding homogeneous catalysts.However little is known about the reaction mechanism and the specialchemical reaction characteristics at the active catalyst centers ofheterogeneous catalysts. It is thus questionable whether the chemistryknown from homogeneous catalysts will be similar or comparable inreaction media catalyzed by heterogeneous catalysts.

The present invention relates to a heterogeneous organotin catalystwhere the active species is chemically fixed by anchoring of theorganotin on a solid macromolecular support. More particular, thepresent invention is concerned with heterogeneous organotin catalysts ona styrene based polymeric support insoluble in most organic basedsolvents useful in esterifications and transesterification reactions. Itis also part of the invention to use special types of heterogeneousorganotin catalysts in chemical reactions like esterification andtransesterification which are unusual compared to catalyst types knownfrom homogeneous catalysis.

Many of the reactions involving functionalized polymeric supportreagents reported in the literature appear to be styrene based. Twosynthetic ways are used: polymerization of a styrenic monomer orgrafting of the active species onto a defined styrene based polymer.

Jiang, et al. in U.S. Pat. No. 5,436,357 and U.S. Pat. No. 5,561,205have described polymeric organotin compounds in which the organotin isattached to a styrene based polymer made by polymerization offunctionalized styrene based organotin monomers. Although thecorresponding organotin catalysts obtained by polymerization lead topolymers with high loading, the inaccessibility of some tins and adifficult control of polymer characteristics during the polymerizationreaction remain the main difficulties and drawbacks of this syntheticroute. These last points can be avoided by the grafting of the activespecies directly on a defined polystyrene. First Weinshenker (J. Org.Chem., 1975, 1966) reported such a synthesis in which the tin atoms weredirectly linked to the phenyl group through a weak bond. Hershberger (J.Polym. Sci., 1987, 219) and Neumann (J. Org. Chem., 1991, Vol. 56, No.21, 5971-5972) describe the introduction of an ethylenic spacer betweenthe active site and the polymer. However, in all these examples, the tinwas in labile positions resulting in a labile chemical bond with highleaching of the organotin species. Mercier (Organometallics, 2001, 958)reports tin-functionalized polystyrenes but limits his synthesis totransesterification tests of grafted diphenyl- and dichloro tin species.

The present invention relates to heterogeneous styrene based organotincatalysts with a suitable spacer between the polymer (polystyrene) andthe tin functionality efficient in preventing cleavage of the tin bondand resulting in low tin pollution levels which show unexpected highcatalytic potentials in esterification and transesterification reactionsand provide excellent possibility to recycle and re-use of the catalyticactive organotin species.

The present invention seeks to provide

-   1. a tetravalent organotin compound wherein at least one ligand is    an organic polymer-   2. an insoluble polymer which acts as a heterogeneous catalyst,    containing a chemically fixed organotin compound-   3. a process for the preparation of the above mentioned insoluble    copolymer which acts as a heterogeneous catalyst-   4. a process for conducting esterification or transesterification    reactions applying such heterogeneous catalyst containing a    chemically fixed organotin compound.

According to the present invention it provided are compositions and/orcompounds defined by the formulas X1 to X3:

wherein Z=a spacer group like —(CH₂)_(m)—

with Y being an insoluble copolymer with

with A being a repeating unit and A=B or C or the end-group of a polymerchain, like CH₃, H or alkylphenyl or the tin residue of X1 to X3

with B being a repeating unit and B=

with C being a repeating unit and C=

with m=2-24

with n=0.01-15% (mol/mol)

with R¹, R², R³ are independently selected from a halogen (such aschloro, bromo, iodo or fluoro), C1-C18 alkyl, C1-C18 alkylene, phenyl,vinyl, allyl, naphthyl, aralkyl such as C1-C18 alkyl phenyl, Z, and atleast one R¹, R², R³ is a halogen (such as chloro, bromo, iodo orfluoro)

with R⁴ being C1-C18 alkyl, C1-C18 alkylene, phenyl, vinyl, allyl,naphthyl, aralkyl such as C1-C18 alkyl phenyl

with R⁵, R⁶ are independently selected from a halogen (such as chloro,bromo, iodo or fluoro), C1-C18 alkyl, C1-C18 alkylene, phenyl, vinyl,allyl, naphthyl, aralkyl such as C1-C18 alkyl phenyl, Z, and at leastone R⁵, R⁶ is a halogen (such as chloro, bromo, iodo or fluoro). Allresidues R¹ to R⁶ may also be—if applicable—linear or branched.

According to the subject matter invention the proviso applies, that if mequals 4 or 6 the residues R1 and R2 are not chlorine and R3 is not abutyl substituent. Those compounds may be applied according to theinvention only in the esterification reactions.

The organic spacer length m is preferably 4 (butyl) or 11 (undecyl). Thecopolymer backbone is preferably a phenyl-group containing copolymer,more preferably a polystyrene-based polymer.

The polymeric support of the compositions of matter is apolystyrene-based polymer. However, other phenyl-group containingcopolymers can also be used (examples are, but not limited to:acrylnitril-butadien-styrene copolymers, methylmethacrylate-butadien-styrene copolymers, polyphenylenether(co)polymers, polyethylene terephthalate, polyphenylen sulfide,polyurethanes and polyamides). It has been found that crosslinkedpolystyrene polymers are particularly useful as support material for theheterogeneous catalysts of the present invention. Whereas it is possibleto use a variety of crosslinking agents like ethylene glycoldimethacrylate, trimethylolpropane trimethacrylate, divinyl toluene,trivinyl benzene and the like it is preferred to use divinylbenzene ascrosslinking comonomer in the polystyrene-based polymer support. Thus itis preferred to use poly(styrene-co-divinylbenzene) as support polymerfor the preparation of the heterogeneous catalysts as the composition ofmatter. The polymeric backbone bears end-groups at the end of thepolymer chain selected from hydrogen, alkyl, alkylphenyl, saturatedvinyl monomer units/compounds applied in the polymerization step,derived from the groups like e.g. vinyl, styrene, vinylbenzene and/ordivinylbenzene, ethers, butadiene, methacrylate.

The divinylbenzene content in the copolymer can vary between wideranges, however it is preferred to use a poly(styrene-co-divinylbenzene)copolymer with an amount of divinylbenzene between 0.01 and 15% (m/m)and particularly between 0.2 and 6% (m/m). It has been found that thepoly(styrene-co-divinylbenzene) copolymer support material should beapplied for the production of the heterogeneous catalysts in amorphology of small beads, typically with sizes between 20 and 1000mesh.

Before using the polystyrene-co-divinylbenzene) copolymer as supportingmaterial it should be prepared and cleaned by a suitable washingprocedure. Different solvents and media can be used like NaOH (1M); HCl(1M); NaOH (2M)/dioxane (2/1); HCl (1M)/dioxane (2/1); H₂O; DMF, HCl(2M)/MeOH (1/2); MeOH/CH₂Cl₂ (3/2); MeOH/CH₂Cl₂ (1/2); MeOH/CH₂Cl₂(1/9); cyclohexane. It is preferred to use these media successively toobtain a clean copolymer support. The polymer should be dried at 65° C.under vacuum before preparing the grafted heterogeneous catalysts.

It is advantageous to use metal organic reagents for obtaining a highconversion grafting reaction. It is preferred to substitute aphenyl-hydrogen in the poly(styrene-co-divinylbenzene) copolymer by asuitable metal like Li, Na, K, Mg by organic metalation reactions whichare well known by those skilled in the art. For example, one may use asolution of butyl lithium in an inert solvent like hexane, heptane orcyclohexane for a lithiation of the phenyl rings of thepoly(styrene-co-divinylbenzene) copolymer.

Generally the grafting agent should be a molecule which can easily reactwith the metallated poly(styrene-co-divinylbenzene) copolymer likehalogenated substances. We have found that α,ω-dihalogen alkanes areadvantageous as spacer bridge building agents and therefore graftingprecursor. Preferably α,ω-chloro-bromo alkanes can be used with chainlengths as desired for a suitable spacer bridge between thepoly(styrene-co-divinylbenzene) copolymer and the active tin species inthe heterogeneous catalyst. Examples for such compounds are1-bromo-3-chloro propane, 1-bromo-4-chloro butane, 1-bromo-5-chloropentane, 1-bromo-6-chloro hexane, 1-bromo-10-chloro decane,1-bromo-11-chloro undecane, 1-bromo-12-chloro dodecane. Preferably thebutyl- or undecyl-α,ω-chloro-bromoalkanes are used, such as1-bromo-4-chloro butane or 1-bromo-11-chloro undecane.

The grafting of the active tin species on thepoly(styrene-co-divinylbenzene) copolymer can be made by a couplingreaction between the ω-haloalkane substituted copolymer and a suitabletin compound. It is preferred to use an organotin hydride which can beobtained by reaction of the corresponding organotin iodide with ahydrogenating agent like NaBH₄.

The organotin iodide can be prepared by reaction of a phenyl substitutedorganotin compound and iodide. When starting with commercially availableorganotin chlorides like monomethyltin trichloride, dimethyltindichloride, tributyltin chloride, monobutyltin trichloride, dibutyltindichloride, monooctyltin trichloride, dioctyltin dichloride,monododecyltin trichloride, didodecyltin dichloride, monocyclohexyltintrichloride, dicyclohexyltin dichloride it is possible to obtain thecorresponding phenyl substituted organotin species by a Grignardreaction with phenyl magnesium chloride which is known in literature andby those skilled in the art.

The organotin hydride when reacted with butyl lithium in an inertsolvent like hexane or tetrahydrofuran forms a corresponding organotinlithium derivative which easily reacts with the ω-haloalkane substitutedcopolymer to form the grafted organotin compound on thepoly(styrene-co-divinylbenzene) copolymer as the composition of matterof the present invention.

It is possible to remove phenyl groups at the active tin species graftedon the poly(styrene-co-divinylbenzene) copolymer by reaction of thecorresponding copolymer with a solution of hydrogen chloride inmethanol. Thus it is possible to obtain heterogeneous organotincatalysts with varying numbers of halogen groups at the active tinspecies grafted on the copolymer (monohalogen substituted organotin,dihalogen substituted organotin, trihalogen substituted organotin).

The halogen substituted organotin groups grafted on thepoly(styrene-co-divinylbenzene) copolymer can be transferred into thecorresponding halogen substituted distannoxanes or tin oxides byreaction with methanol in water or aqueous sodium hydroxide intetrahydrofuran.

The process for the preparation of the organotin compounds according tothe invention comprises therefore the following steps:

-   -   (a) substitution of a phenyl-hydrogen in a        poly(styrene-co-divinylbenzene) copolymer by a suitable metal        like Li, Na, K, Mg by organic metalation reactions,    -   (b) in a second step    -   reacting a dihalogen spacer molecule by with the metalated        poly(styrene-co-divinylbenzene) copolymer as of step (a),    -   (c) and grafting in a third step the spacer-halogen        poly(styrene-co-divinylbenzene) copolymer with a organotin        hydride to yield the organotin compounds.

Preferably supported heterogeneous organotin compounds of formula X1with a butyl or undecyl spacer group, equivalent to m=4 or m=11 and R1to R3 to be chlorine can be employed as catalysts for esterificaton ortransesterification reactions. Other preferred supported heterogeneousorganotin compounds useful in such reactions are (a) polymer-grafteddihalogen alkyl tin or (b) polymer-grafted dialkyltin chloridecompounds, preferably characterized for (a) by formula X1 having a butylor undecyl spacer group, equivalent to m=4 or m=11 and R1 and R2 to bechlorine and R3 to be all structural isomers of butyl or octyl or for(b) compounds of formula X1 with m=4 or m=11 and R1 and R2 to be allstructural isomers of butyl or octyl and R3 to be chlorine. Mostpreferred are supported heterogeneous organotin compounds of formula X1with a butyl spacer group, equivalent to m=4 and R1 to R3 to bechlorine.

Referring to formula X2 preferred supported heterogeneous organotincompounds with a butyl or undecyl spacer group, equivalent to m=4 orm=11 and R4 to be butyl are useful catalysts for esterificaton ortransesterification reactions.

Referring to formula X3 preferred supported heterogeneous organotincompounds with a butyl or undecyl spacer group, equivalent to m=4 orm=11 and R5 to be butyl and R6 to be chlorine are useful catalysts foresterificaton or transesterification reactions.

Esterification reactions using the catalyst may be accomplished by theusual reaction between an acid or acid anhydride and an alcohol in anorganic medium in the presence of the catalyst according to the presentinvention. Reaction temperatures are usually between 50° C. and 280° C.,reaction time can vary between 0.5 and 24 hours. At the end of thereaction the liquid reaction products can be separated from the solidheterogeneous organotin catalysts by filtration or decantation orsedimentation step or any other mean of phase separation. The catalystscan be washed if desired and then reused again in the esterificationreaction. A fresh charge of the reaction educts may then be added andthe catalysts can be reused again for several times.

Transesterification reactions using the catalyst may be accomplished bythe typical reaction between an ester and an alcohol in an organicmedium in the presence of the catalyst according to the presentinvention. Reaction temperatures are usually between 50° C. and 200° C.,reaction time can vary between 0.5 and 24 hours. At the end of thereaction the liquid reaction products can be separated from the solidheterogeneous organotin catalysts by filtration or decantation orsedimentation step or any other mean of phase separation. The catalystscan be washed if desired and then reused again in thetransesterification reaction. A fresh charge of the reaction educts maythen be added and the catalysts can be reused again for several times.

It is part of the present invention that the grafted organotin specieson the poly(styrene-co-divinylbenzene) copolymer support show unusualand excellent catalytic properties and potentials. In contrast toesterification and transesterification reactions catalyzed byhomogeneous organotin compounds we have found that nearly all differentheterogeneous organotin catalysts of the present invention have a highcatalytic potential in the corresponding reaction.

For example a grafted organotin dihalogenide (i.e. a dialkyltin)according to the present invention is a good catalyst in esterificationreactions which is not the case in homogeneous catalysis.

Also, we have found that a grafted organotin trihalogenide (i.e. amonoalkyltin) according to the present invention is a good catalyst intransesterification reactions which is not the case in homogeneouscatalysis. These catalysts show unexpectedly high catalytic potentialscompared to results reported for grafted dichloro tin species (i.e. adialkyltin dichloride) by Mercier (Organometallics, 2001, 958) who usesthe same transesterification test but with much longer reaction times).Moreover also grafted organotin monohalogenides (i.e. a trialkyltin)according to the present invention show good catalytic potentials inesterification and transesterification. Mercier discloses comparabledichloro compounds requiring transesterification reaction times of atleast 24 hours even in the first run.

The present application discloses catalysts reducing the reaction timeto only 4 hours at 80° C., being distinct below the reflux conditionsMercier applies. It has been thus unexpectedly found, that the reactiontime is even more dramatically reduced at extremely high conversionrates of at least 95% (in most cases higher than 99%) using compounds offormula X1 in esterification reactions.

Furthermore it is to be considered inventive that the compoundsdisclosed in the present application are easy to recycle and re-use byrepeated phase separation from esterification or transesterificationreaction mixtures, repeated washing and re-suspension in fresh reactionmixtures.

Further subject of the present invention are esters produced byesterification or transesterification reactions by use of organotincompounds as defined by the formulas X1 to X3 following a process asdefined before, comprising a mixture of two esters (for thetransesterification reaction) or comprising an alcohol and an acid(organic carboxylic acid—for the esterification) and an amount of 0.001to 1 mol % of the catalyst at a reaction temperature of 50° C. to 200°C. for the transesterification and 50-280° C. for the esterificationprocess, characterized by a tin content below 50 ppm for thetransesterification products and below 550 for most of theesterification products. The higher amount for the esterificationproducts is mainly due to the higher conversion temperature resulting inmore—extractable and tin-containing—decomposition by-products.

The following examples are presented to illustrate but not to limitvarious embodiments of the present invention.

EXAMPLES Synthesis of Organotin Precursors

Synthesis of Dibutyldiphenyltin

In a three-necked flask, a solution of bromobenzene (62.8 g, 400 mmol)in diethyl oxide was added on magnesium (12 g, 500 mmol) covered withdry diethyl oxide. When the addition was completed, the mixture wasrefluxed during one hour. This solution was then added to dibutyltindichloride (30 g, 98.8 mmol) in 150 mL of diethyl oxide and refluxed for3 hours. The mixture was hydrolysed with a minimum of water, washed witha saturated aqueous solution of sodium chloride, dried over magnesiumsulphate and concentrated. Purification by liquid chromatography onsilica gel (eluent:petroleum ether) gave an oil (28.6 g, 74.5 mmol).

Yield: 75%

¹H NMR (CDCl₃) δ: 7.69 (4H, bs); 7.50 (6H; bs); 1.83 (4H, m); 1.53 (8H,bs); 1.08 (6H, t, J=7.3 Hz).

¹³C NMR (CDCl₃) δ: 140.78; 137.23; 128.69; 29.44; 27.84; 14.12; 10.72.

¹¹⁹Sn NMR (C₆D₆) δ: −71.7 ppm.

Synthesis of Dibutylphenyltin Iodide

In a three-necked flask protected from light, dibutyl diphenyltin (10 g,25.9 mmol) was solubilized in 50 mL of dry methanol. A solution ofiodine (6.04 g, 23.76 mmol) in methanol was then added slowly. Afterstirring at room temperature for 16 hours, methanol was eliminated undervacuum. The residue was dissolved in petroleum ether and washed with asaturated aqueous solution of sodium thiosulphate. Organic layers werewashed with a saturated sodium chloride solution and dried over MgSO₄.Solvent was evaporated and the crude product was distilled using aKugelrohr apparatus (rotating glass oven for fractionating distillationof small sample volumes at 60° C. A colourless oil was obtained (10.5 g,24.0 mmol).

Yield=93%

¹H NMR (CDCl₃) δ: 7.50 (2H, bs), 7.17 (2H, bs), (12H), 1.05 (6H, t,J=7.3 Hz)

¹¹⁹Sn NMR (CDCl₃) δ: 13.9 ppm

Synthesis of Dibutylphenyltin Hydride

In a Schlenk tube, a suspension of NaBH₄ (1.96 g, 51.9 mmol) in 50 mL ofabsolute ethanol was cooled at 0° C. under nitrogen. A solution ofBu₂SnPhI (15.1 g, 34.6 mmol) in ethanol was then added slowly understirring. After 3 hours at room temperature in the dark, petroleum etherwas added, the solution was washed with water and dried over MgSO₄.Solvents were eliminated under reduced pressure and the residue wasdistilled under high vacuum. A colourless oil was obtained (7.2 g, 30.8mmol).

Yield: 89%

¹H NMR (C₆D₆) δ: 7.29 (2H, t, J=6 Hz), 7.17 (3H, t, 6 Hz), 5.80 (1H, m),1.56 (4H, m), 1.41 (4H, m), 1.19 (4H, m), 0.96 (6H, t, J=7.3 Hz)

¹³C NMR (C₆D₆) δ: 139.27; 137.24; 128.52; 128.29; 127.97; 127.65; 29.88;27.35; 13.79; 9.43.

¹¹⁹Sn NMR (C₆D₆) δ: −111.0 ppm.

Synthesis of Butyltriphenyltin

In a three-necked flask, a solution of 1-bromobutane (34.25 g, 250 mmol)in diethyl oxide was added on magnesium (7.3 g, 300 mmol) covered withdry diethyl oxide. When the addition was completed, the mixture wasrefluxed during one hour. This solution was then added to triphenyltinchloride (42.6 g, 110 mmol) in 150 mL of diethyl oxide and refluxed for3 hours. The mixture was hydrolysed with a minimum of water, washed witha saturated aqueous solution of sodium chloride, dried over magnesiumsulphate and concentrated. Crystallization of the crude product inmethanol gave a white solid (32.3 g, 93 mmol).

Yield: 85%

mp=64.8° C.

¹H NMR (CDCl₃) δ: 7.46 (6H; m; ²J(Sn—H)=54 Hz; H_(a,d)); 7.28 (9H; m;H_(b,e,d)); 1.7 (2H; m; H₃); 1.6 (2H; m; H₄); 1.44 (2H; sext; ³J=7.1 Hz;H₂); 0.91 (3H; t; ³J=7.1 Hz; H₁)

¹³C NMR (CDCl₃) δ: 138.6 (C_(i), ¹J(Sn—C)=483/460 Hz); 136.5 (C_(b,d),³J(Sn—C)=35.1 Hz); 128.2 (C_(c), ⁴J(Sn—C)=10.4 Hz); 127.9 (C_(a,e),²J(Sn—C)=17.6 Hz); 28.3 (C₃, ²J(Sn—C)=21.8 Hz)); 26.8 (C₂, ³J(Sn—C)=64.6Hz); 13.0 (C₁, ⁴J(Sn—C)=15.4 Hz); 10.3 (C₄, ¹J(Sn—C)=398/380 Hz).

¹¹⁹Sn NMR (C₆D₆) δ: −99.3.

Synthesis of Butyldiphenyltin Iodide

In a three-necked flask protected from light, butyltriphenyltin (21.05g; 51.8 mmol) was dissolved in 50 mL of dry methanol. A solution ofiodine (12.06 g; 47.5 mmol) in methanol was then added slowly. Afterstirring at room temperature during 16 hours, methanol was eliminatedunder vacuum. The residue was dissolved in petroleum ether and washedwith a saturated aqueous solution of sodium thiosulphate. Organic layerswere washed with a saturated NaCl solution and dried over MgSO₄. Solventwas evaporated and the crude product was distilled using a Kugelrohrapparatus at 60° C. A colourless oil was obtained (22.2 g, 48.6 mmol).

Yield=94%

¹H NMR (CDCl₃) δ: 7.88 (6H, m, H_(b,c,d)); 7.46 (6H, m, H_(a,d)); 2.31(2H, m, AA′BB′, H_(4.3)); 1.89 (2H, sext, ³J=81 Hz, H₂); 1.41 (3H, t,³J=8.1 Hz, H₁)

¹³C NMR (CDCl₃) δ: 137.2 (C_(f), ¹J(Sn—C)=130 Hz); 136.5 (C_(a,e),²J(Sn—C)=45.7 Hz); 130.0 (C_(c), ⁴J(Sn—C)=26.3 Hz); 128.9 (C_(b,d),³J(Sn—C)=55.3 Hz); 28.9 (C₃, ²J(Sn—C)=27.6 Hz); 26.7 (C₂, ³J(Sn—C)=74.4Hz); 17.2 (C₄, ⁴J(Sn—C)=399/381 Hz); 13.7 (C₁)

¹¹⁹Sn NMR (C₆D₆) δ: 51.8 ppm

Synthesis of Butyldiphenyltin Hydride

In a Schlenk tube, a suspension of NaBH₄ (1.31 g, 34 mmol) in 50 mL ofabsolute ethanol was cooled at 0° C. under nitrogen. Then, a solution ofBuSnPh₂I (22.2 g) in ethanol was added slowly under stirring. After 3hours at room temperature in the dark, petroleum ether was added, thesolution was washed and dried over MgSO₄. Solvents were eliminated underreduced pressure. A colourless oil was obtained (6.67 g, 0.02 mol).

Yield: 92%

¹H NMR (C₆D₆) δ: 7.86 (6H, m, H_(a,d), ¹J(Sn—H)=55.4 Hz); 7.5 (6H, m,H_(b,c,d)); 6.4 (1H, s, ¹J(Sn—H)=1795/1713 Hz, Sn—H); 1.64 (2H, m,³J=7.3 Hz, H₂); 1.42 (4H, m, AA′BB′, H_(4,3)); 0.9 (3H, t, ³J=7.3 Hz,H₁)

¹³C NMR (CDCl₃) δ: 139.3 (C_(b,d), ³J(Sn—C)=36.2 Hz); 137.5 (C_(f),¹J(Sn—C)=201.3/188.7 Hz); 129.2 (C_(c), ⁴J(Sn—C)=11.4 Hz); 128.9(C_(a,e), ²J (Sn—C)=22.9 Hz); 29.6 (C₃, ²J(Sn—C)=22.8 Hz); 27.48 (C2,³J(Sn—C)=61.1 Hz); 13.9 (C₁); 10.4 (C₄, ¹J(Sn—C)=312/296 Hz)

¹¹⁹Sn NMR (C₆D₆) δ: −136.4 ppm.

Synthesis of Tricyclohexyltin Chloride

In a 500 mL three-necked flask, trimethylsilyl chloride (170 g, 109mmol) was added to tricyclohexyltin hydroxide (80 g, 133 mmol) andheated at reflux during 18 hours. After distillation of trimethylsilylchloride in excess and hexamethyldisiloxane under reduced pressure, thecrude product was recrystallized in petroleum ether. White needles wereobtained (39.82 g, 79.6 mmol).

Yield: 73%

¹H NMR (CDCl₃) δ: 2.1-1.31 (33H, ma)

¹³C NMR (CDCl₃) δ: 34.25; 31.56; 29.27; 27.22.

¹¹⁹Sn NMR (CDCl₃) δ: 70.3 ppm

Synthesis of Tricyclohexyltin Hydride

A mixture (400 mL) of diethyl oxide:water 1:1 was cooled at 0° C. undernitrogen in a three-necked flask of 1 L. Sodium borohydride (3 g, 79.4mmol) and then tricyclohexyltin hydroxide (30 g, 62.2 mmol) weresuccessively and carefully added. After addition of 100 mL of diethyloxide, the mixture was stirred 2 days at room temperature. Afterseparation, the organic layer was dried over magnesium sulphate andevaporated under reduced pressure. The crude product was distilled underhigh vacuum to afford, a colourless oil (23.23 g; 63 mmol).

Yield: 81%

¹H NMR (CDCl₃) δ: 5.29 (s, 1H); 2.82-1.39 (bs, 33H).

¹³C NMR (CDCl₃) δ: 31.56; 27.57; 25.62; 24.37.

¹¹⁹Sn NMR (CDCl₃) δ: −92.8 ppm.

Syntheses of Organotin Supported Compounds

Synthesis of P4Cl

CombiGel XE-305 [Aldrich, 1% cross-linkedpoly(styrene-co-divinylbenzene) copolymer, 50-100 mesh, 150-300 μmbeads]═P—H (6.3 g) was covered with 45 mL of dry cyclohexane. Freshlydistilled TMEDA (N,N,N′,N′-Tetramethylethylen diamine, 9 mL; 60 mmol)and n-butyllithium (2.5 M in hexanes) (30 mL, 75 mmol) were successivelyadded. The mixture was stirred at 65° C. during 4 hours. Residualbutyllithium was eliminated by transfer with a canula and the polymerwas washed twice with dry cyclohexane. Then, the treatment withbutyllithium was repeated. The lithiated polymer P—Li was washed severaltimes with dry THF, under nitrogen, until no more butyllithium waspresent in the washing solution α-naphtylphenylamine test). The pinkpolymer P—Li was covered with 30 mL of anhydrous THF (tetrahydrofuran)and a solution of 1-bromo-4-chlorobutane (13.2 g, 60 mmol) in THF (30mL) was added at 0° C. After 6 hours at room temperature, the polymerwas washed once with 50 mL of a mixture THF/H₂O (1/1); four times with50 mL of THF and twice with 50 mL of ethanol, and dried. 8.9 g of P4Clwere obtained.

Three batches were prepared:

P4Cl-1: Percentage of functionalization T=33.4%, Degree offunctionalization N^(Cl)=2.53 mmol/g

Microanalyses (%): C, 83.22; H, 8.03; Cl, 8.84; Br, 0.18

P4Cl-2: T=23%, N^(Cl)=1.85 mmol/g

Microanalyses (%): C, 83.33; H, 8.21; Cl, 6.55; Br, 0.32

P4C₁₋₃: T=22.8%, N^(Cl)=1.83 mmol/g

Microanalyses (%): C, 81.50; H, 8.14; Cl, 6.50; Br, 0.94

Synthesis of P11Cl

The synthesis route for P11Cl is the same as for P4Cl, Br(CH₂)₁₁Cl willbe used instead of 1-bromo-4-chlorobutane.

Synthesis of Br(CH₂)₁₁Cl

In a 250 mL three-necked flask, 11-bromoundecanol (10 g, 39.8-mmol),pyridine (2 mL, 24.7 mmol) and thionyl chloride (10 mL, 137 mmol) weresuccessively introduced. The solution was stirred at room temperatureand the reaction was followed by IR. After disappearance of the OH band,the mixture was hydrolysed carefully by addition of water, the aqueouslayer was extracted three times with diethyl oxide. The organic layerswere washed successively with a 10% HCl aqueous solution, water, asaturated aqueous solution of NaHCO₃ and water until neutrality. Afterdrying over MgSO₄ and elimination of solvents under reduced pressure,the oil was filtered on silica gel (eluent: pentane). A colourless oilwas obtained (10.15 g, 35 mmol).

Yield: 88%.

¹H NMR (CDCl₃) δ: 3.50 (2H, t, J=Hz); 3.38 (2H, t, J=Hz); 1.78 (4H, m);1.38 (4H, m); 1.26 (10H, bs).

¹³C NMR (CDCl₃) δ: 45.17; 34.03; 32.86; 32.68; 29.45; 29.42; 28.90;28.78; 28.19; 26.90.

Stannylation Reaction

General procedure. Diisopropylamine (1 eq.) and n-Buli (2.5 M inhexanes) (1 eq.) were successively added to 20 mL of dry THF at 0° C.After 5 minutes of stirring, the appropriate hydride (1 eq.) was addedslowly and the mixture was stirred 30 min further. This solution ofR₃SnLi (in large excess) was slowly added to P4Cl (6 g) suspended in 40mL of dry THF. The mixture was stirred for 15 hours at room temperature.After filtration, the polymer was washed with 40 mL of THF/H₂O (50/50),40 mL of THF (6 times) and 20 mL of ethanol (twice).

Solid-state NMR Microanalysis: found (%) Functionalization ¹¹⁹Sn C H SnCl T (%) N^(Sn) (mmol/g) P4SnBu₂Ph — 74.11 8.52 13.80 0.25 21 1.16P4BuSnPh₂ −76.7 77.24 7.49 14.00 0.16 25 1.18 P4SnCy₃ — 77.57 8.65 13.111.43 22 1.10 P11SnBu₂Ph — 82.96 9.28 1.6 4.26 1.6 10⁻³ P11BuSnPh₂ —77.95 8.53 10.90 1.92 17 0.92 P11SnCy₃ — 75.84 9.32 13.49 <0.04 29 1.14Synthesis of P4SnBu₂Cl

A solution of HCl in methanol (2.48 mol*l⁻¹, 10 mL) was added toP4SnBu₂Ph (8 g) suspended in 40 mL of absolute methanol. The mixture washeated at 65° C. during 24 hours. After filtration, the polymer waswashed 8 times with 30 mL of methanol and dried, 7.8 g of P4SnBu₂Cl wereobtained.

Microanalysis (%): C, 71.59; H, 7.93; Cl, 4.22; Sn, 14.71.

T=21.9%, N^(Cl)=1.19 mmol/g, N^(Sn)=1.24 mmol/g

¹¹⁹Sn solid-state NMR δ: 139.1 ppm

Synthesis of P4SnBuCl₂

A solution of HCl in methanol (2.48 mol*l⁻1, 20 mL) was added toP4SnBuPh₂ suspended in 40 mL of absolute methanol. The mixture washeated at 65° C. during 24 hours. After filtration, the polymer waswashed 8 times with 30 mL of methanol.

Microanalysis (%): C, 66.92; H, 6.90; Cl, 9.63; Sn, 15.50

T=25.1%, N^(Cl)=2.72 mmol/g, N^(Sn)=1.31 mmol/g

¹¹⁹Sn solid-state NMR δ: 200.4 ppm

Synthesis of P4SnCl₃

A solution of tin chloride (IV) (1 eq.) in toluene was slowly added to asuspension of PnSnCy₃ in toluene. After 48 hours in the dark, thepolymer PnSnCl₃ was filtered and washed eight times with pentane andtwice with ethanol.

Synthesis of P4SnClO

Water (2 eq.) was added to a suspension of P4SnBuCl₂ (1 g) in methanolat 65° C. After 6 hours, the polymer was filtered and the treatment withwater was repeated and heated at 65° C. during 18 hours. Then, thepolymer was washed 8 times with methanol and dried.

¹¹⁹Sn solid-state NMR δ: 175 ppm

Synthesis of P4SnO

An aqueous solution of potassium hydroxide (10 eq., 4M) was added to asuspension of polymer P4SnBuCl₂ (300 mg) in 20 mL of dry THF at 65° C.After 24 hours, the polymer was filtered and washed successively with amixture THF/H₂O (50/50), THF and ethanol.

Synthesis of P11SnBu₂Cl, P11SnBuCl₂, P11SnCl₃, P11SnClO, P11SnO

The synthesis of the grafted heterogeneous organotin catalysts with aspacer length of 11 CH₂-groups can be performed according to thecorresponding P4 compounds.

General Procedures of Catalysis Test Reactions:

Procedure 1.

-   -   Esterification Test Reaction: For evaluation of the catalytic        potential of the heterogeneous catalysts in esterification        reactions an appropriate test reaction has been developed and        used. In a reaction vessel under a nitrogen atmosphere phthalic        anhydride (1 eq.) was reacted with 2-ethyl hexanol (2 eq.) at        220° C. for 4 hours after addition of appropriate amounts of the        catalyst [0.1 mol % as tin]. The amount of unreacted acid at the        end of the reaction, expressed in terms of Acid Number is        determined. The catalyst can be separated from reaction products        and recycled by carrying out another esterification reaction for        an evaluation of reuse capabilities of the catalyst. At the end        of each reaction the liquid reaction products were separated        from the solid heterogeneous organotin catalysts by filtration.        The catalysts were washed and then reused again in the        esterification reaction. The tin leaching from the catalyst into        the reaction products can be analyzed (tin content).

Procedure 2.

-   -   Transesterification Test Reaction: For evaluation of the        catalytic potential of the heterogeneous catalysts in        transesterification reactions an appropriate test reaction has        been developed and used. In a reaction vessel under a nitrogen        atmosphere ethyl acetate (1 eq.) was reacted with the alcohol        1-octanol (7 eq.) at 80° C. for 4 hours after addition of        appropriate amounts of the catalyst [0.1 mol % as tin]. The        assessment and analysis of the reaction (ratio initial        alcohol/obtained ester, amount of transesterified ester        compound) is possible by GC (quantitative method). The catalyst        can be separated from reaction products and recycled by carrying        out another transesterification reaction for an evaluation of        reuse capabilities of the catalyst. At the end of each reaction        the liquid reaction products were separated from the solid        heterogeneous organotin catalysts by filtration. The catalysts        were washed and then reused again in the transesterification        reaction. The tin leaching from the catalyst into the reaction        products can be analyzed (tin content).

Procedure 3.

-   -   Tin Leaching: The reaction products of the test reactions and        recycle test series have been analyzed with respect to their        organotin content. The leaching of tin compounds out of the        heterogeneous catalysts was checked and measured by a suitable        Soxhlet extraction procedure (extracting agent: ethyl acetate,        extraction time: 6 h).

Results Procedure 1—Esterification Test Reaction

Reaction Tin-Content Heterogeneous Catalyst Acid Number Rate [ppm]P4SnBu₂Cl 0.6 99.88 305 P4SnBu₂Cl (recycled) 2.3 99.54 207 P4SnBu₂Cl(recycled) 2.4 99.52 212 P4SnBu₂Cl (recycled) 11.9 97.63 68 P4SnCl₃ 2.399.54 554 P4SnCl₃ (recycled) 2.7 99.46 not detectable P4SnCl₃ (recycled)4.4 99.12 not detectable P4SnCl₃ (recycled) 5.9 98.82 60 P4SnBuCl₂ 1.199.78 188 P4SnBuCl₂ (recycled) 0.9 99.82 19 P4SnBuCl₂ (recycled) 1.499.72 62 P4SnBuCl₂ (recycled) 4.6 99.08 23 P4SnClO-1 1.4 99.72 104P4SnClO-1 (recycled) 0.8 99.84 104 P4SnClO-1 (recycled) 1.6 99.68 86P4SnClO-1 (recycled) 2.5 99.50 129 P4SnO 1.5 99.70 269 P4SnO (recycled)0.5 99.90 66 P4SnO (recycled) 2.8 99.44 275 P4SnO (recycled) 0.6 99.88155 P11SnBuCl₂ 0.5 99.90 149 P11SnBuCl₂ (recycled) 1 99.80 86 P11SnBuCl₂(recycled) 0.9 99.82 107 P11SnBuCl₂ (recycled) 4.1 99.18 198 P11SnCl₃1.8 99.64 630 P11SnCl₃ (recycled) 1.3 99.74 not detectable P11SnBu₂Cl2.1 99.58 44 P11SnBu₂Cl (recycled) 4.0 99.20 16 P11SnBu₂Cl (recycled)5.1 98.98 9 P11SnClO 1.2 99.76 306 P11SnClO (recycled) 1.5 99.70 135P11SnClO (recycled) 3.2 99.36 139 P11SnClO (recycled) 7.5 98.51 187P11SnO 1.2 99.76 not detectable P11SnO (recycled) 1.4 99.72 115 P11SnO(recycled) 4.3 99.14 99 P11SnO (recycled) 4.3 99.14 265 P11SnBu₂Cl 0.799.86 289 P11SnBu₂Cl (recycled) 0.4 99.92 62 P11SnBu₂Cl (recycled) 5.698.88 215

Results Procedure 2—Transesterification Test Reaction

Ethyl 1-Octyl Tin Content Heterogeneous Catalyst Ethanol acetate1-Octanol acetate Conversion [ppm] P4SnBu₂Cl 0.42 85.44 15.98 1.41 6.123 P4SnBu₂Cl (recycled) 1.21 83.87 13.77 4.06 17.61 3 P4SnBu₂Cl(recycled) 1.3 80.39 14.02 4.89 21.21 4 P4SnBu₂Cl (recycled) 2.01 81.3812.53 6.79 29.45 7 P4SnBu₂Cl (recycled) 1.84 82.63 11.93 6.47 28.06 9P4SnBu₂Cl (recycled) 2.29 80.31 9.68 8.55 37.08 9 P4SnBu₂Cl 0.87 83.2615.42 3.07 13.32 not (after extraction) detectable P4SnBuCl₂ (*) 0.2887.68 16.98 0.90 3.90 3 P4SnBuCl₂ (recycled) (*) 0.52 84.03 16.15 1.847.98 3 P4SnBuCl₂ (recycled) (*) 0.52 81.79 17.12 2.06 8.94 7 P4SnBuCl₂(recycled) (*) 0.84 80.63 14.85 3.18 13.79 8 P4SnBuCl₂ (recycled) (*)1.29 83.3 13.49 4.5 19.52 8 P4SnBuCl₂ (recycled) (*) 1.24 78.64 14.596.03 26.15 6 P4SnBuCl₂ (recycled) (*) 1.52 75.51 16.03 8.43 36.56 9P4SnCl₃ (after extraction) 4.86 81.73 4.42 16.19 70.22 8 P4SnCl₃ 3.6874.19 7.02 14.44 62.63 23 P4SnCl₃ (recycled) 4.21 76.88 5.91 15.11 65.543 P4SnCl₃ (recycled) 3.76 77.38 7.08 13.20 57.25 25 P4SnCl₃ (recycled)3.49 75.30 7.50 14.49 62.85 2 P4SnCl₃ (recycled) 4.20 77.09 6.07 14.3262.11 5 P4SnCl₃ (recycled) 3.87 74.71 6.67 14.72 63.85 4 P4SnCl₃(recycled) 3.62 77.99 7.26 12.70 55.08 2 P4SnCl₃ (recycled) 3.26 80.189.09 11.26 48.84 6 P4SnCl₃ (recycled) 3.29 84.75 7.9 11.23 48.71 9P4SnClO-1 0.53 83.21 15.95 1.96 8.50 2 P4SnClO-1 (recycled) 0.88 84.3013.82 3.15 13.66 5 P4SnClO-1 (recycled) 0.80 84.76 14.86 2.84 12.32 3P4SnClO-1 (recycled) 0.70 78.93 16.21 3.15 13.66 4 P4SnClO-1 (recycled)2.24 81.23 10.75 7.69 33.35 7 P4SnO 0.31 83.96 17.93 1.25 1.58 notdetectable P11SnBuCl₂ 0.58 87.46 16.25 1.67 7.24 2 P11SnBuCl₂ (recycled)0.73 81.27 16.9 3.12 13.53 3 P11SnBuCl₂ (recycled) 1.12 87.77 13.96 3.3414.49 5 P11SnBuCl₂ (recycled) 0.91 75.8 16.89 4.35 18.87 4 P11SnBuCl₂(recycled) 1.48 85.7 12.76 4.57 19.82 5 P11SnCl₃ 2.56 78.16 10.42 9.7242.16 230 P11SnCl₃ (recycled) 3.90 73.05 6.35 16.32 70.79 11 P11SnClO0.22 83.73 17.55 0.87 1.10 not detectable P11SnClO (recycled) 0.21 83.0116.44 0.77 0.97 not detectable P11SnClO (recycled) 0.27 78.33 18.48 1.511.91 not detectable P11SnClO (recycled) 0.98 80.17 16.14 4.11 5.20 6P11SnO 0.21 84.88 16.68 0.68 0.86 not detectable P11SnO (recycled) 0.4683.72 15.6 1.68 2.13 not detectable P11SnO (recycled) 0.32 81.15 17.961.5 1.90 6 (*) comparative example

It should be noted, that the P4SnBuCl₂ according to the Mercierpublication only gives moderate conversion rates under the presentreaction conditions. Especially the P11SnCl₃ and P4SnCl₃ givesignificant higher conversion rates being contrary to the expectationsand therefore being surprising.

Result Procedure 3—Tin Leaching from Heterogeneous Catalysts

Heterogeneous Sn-Content (Extracting Agent) Catalyst [ppm] Sn-Content(Catalyst) P4SnBu₂Cl 3 14.80% P4SnCl₃ 30 15.50% P4SnBuCl₂ 7 11.80%P4SnClO-1 not detectable 11.90% P4SnO not detectable P11SnBuCl₂ notdetectable 11.30% P11SnBu₂Cl not detectable 12.30% P11SnCl₃ 421 15.00%P11SnClO not detectable 16.40% P11SnO not detectable 16.60%

1. A process for the esterification of an aromatic dicarboxylic acid oran ester-forming derivative thereof, and an aliphatic diol or anester-forming derivative thereof, which process comprises reacting thearomatic dicarboxylic acid or an ester-forming derivative thereof, andthe aliphatic diol or an ester-forming derivative thereof, in a reactionmixture comprising an effective amount of an organotin compound of theformula X1, X2, or X3:

wherein Z is (CH₂)_(m)—; m is a number of from 4 to 24; and Y is aninsoluble phenyl-group containing copolymer, R¹, R², R³ areindependently selected from the group consisting of halogen, C₁-C₁₈alkyl, C₁-C₁₈ alkylene, phenyl, vinyl, allyl, naphthyl, and aralkyl,with the proviso that at least one of R¹, R², or R³ is a halogen; R⁴ isC₁-C₁₈ alkyl, C₁-C₁₈ alkylene, phenyl, vinyl, allyl, naphthyl, oraralkyl; R⁵ and R⁶ are independently selected from the group consistingof halogen, C₁-C₁₈ alkyl, C₁-C₁₈ alkylene, phenyl, vinyl, allyl,naphthyl, and aralkyl, with the proviso that at least one of R⁵ or R⁶ isa halogen; with the proviso that when m is 4 or 6, two of R¹, R², and R³are not chlorine.
 2. A process as recited in claim 1 additionallycomprising the step of separating the organotin compound from thereaction mixture by a phase separation means.
 3. A process for theesterification of an aromatic dicarboxylic acid or an ester-formingderivative thereof, and an aliphatic dial or an ester-forming derivativethereof, which process comprises reacting the aromatic dicarboxylic acidor an ester-forming derivative thereof, and the aliphatic dial or anester-forming derivative thereof, in a reaction mixture comprising aneffective amount of an organotin compound resulting from a processcomprising the steps of: (a) reacting a suitable metal with a poly(styrene-co-divinylbenzene) copolymer under conditions effective toreplace the phenyl-hydrogen in the poly(styrene-co-divinylbenzene)copolymer with the suitable metal, to produce a metalatedpoly(styrene-co-divinylbenzene) copolymer; (b) reacting the metalatedpoly(styrene-co-divinylbenzene) copolymer with a dihalogen spacermolecule, under conditions effective to produce a spacer-halogenpoly(styrene-co-divinylbenzene) copolymer, and (c) grafting thespacer-halogen poly(styrene-co-divinylbenzene) copolymer with anorganotin hydride under conditions effective to yield the organotincompound having the formula X1, X2, or X3;

wherein Z is —(CH₂)_(m)—; m is a number of from 4 to 24; and Y is aninsoluble phenyl-group containing copolymer, R¹, R², R³ areindependently selected from the group consisting of halogen, C₁-C₁₈alkyl, C₁-C₁₈ alkylene, phenyl, vinyl, allyl, naphthyl, and aralkyl,with the proviso that at least one of R¹, R², or R³ is a halogen; R⁴ isC₁-C₁₈ alkyl, C₁-C₁₈ alkylene, phenyl, vinyl, allyl, naphthyl, oraralkyl; R⁵ and R⁶ are independently selected from the group consistingof halogen, C₁-C₁₈ alkyl, C₁-C₁₈ alkylene, phenyl, vinyl, allyl,naphthyl, and aralkyl, with the proviso that at least one of R⁵ or R⁶ isa halogen; with the proviso that when m is 4 or 6, two of R¹, R² and R³are not chlorine.
 4. The process of claim 1 wherein R¹, R², R³, R⁵, andR⁶ are halogen or C₄-C₈ alkyl, and R⁴ is C₄-C₈ alkyl.
 5. The process ofclaim 1 wherein R¹, R², R³, R⁵, and R⁶ are chlorine, butyl, or octyl,and R⁴ is butyl.
 6. The process of claim 1 wherein m is a number from 4to 11.